Hilda Lyon – airships, windtunnels and submarines

Hilda Margaret Lyon MA., MSc., AFRAeS. (1896-1946)

Hilda in the 1930s

Hilda Margaret Lyon was born in Market Weighton in 1896, into a family of farmers and grocers. She had 4 older siblings but, out of the whole family, she seems to have been the only one to have travelled and lived out of the area.

Beverley High School today
Educated at Beverley High School, where she was in the first group of pupils, Hilda went on to graduate with a mathematics degree from Newnham College, Cambridge in 1918. Her first job was as an aircraft technical assistant at Siddeley Deasy Motor Company which was making aircraft for the war in Coventry, during which period she spent 6 weeks with the Air Ministry’s “Criticism of strength” department. In 1920 she moved to George Parnall & Co, another aircraft manufacturer. Her first job was on the stresses in the bracing wires of a proposed large biplane bomber, but the war ended long before it even got off the drawing board. Other projects which never got into production were a triplane and the UK’s first attempt at an all metal monoplane.

Hilda, describing her work to colleagues in the Women’s Engineering Society made the point that she might spend a year in detailed experiments, analysis and design, doing countless complex calculations with her slide rule, only to have the project cancelled on the decision of a higher authority. One such project was a large biplane that was being developed for bombing Berlin but the end ot the first world war put a stop to that project.

In 1922 she became an associate fellow of the Royal Aeronautical Society and in 1925 joined the Royal Airship Works in Cardington to work on the stresses for the airship R101.

Airship shed at Farnborough

At Cardington she was in the ‘govoernment team’ (working on the R101) competing with a commercial team (working on the R100) at Howden a few miles from her home town in Yorkshire. The competition was to determine if the state or the commercial sector should design future airships and they were asked to design a huge airship capable of carrying troops to India.
She would later describe herself at this time as a “country bumpkin” entering a foreign country where people spoke a different language but she was intrigued more by the application of her maths than she had been by pure theory at university.
Hilda was one of the scientists who showed that the famous R100 and R101 airships, thought at the time to be the last word in streamlining, were based on a false understanding of the wind tunnel tests. Her work showed that the problem had arisen due to the small size of the models used in the wind tunnels and she was able to prove that a rounder shape at the front, tailing off to a point, like a ‘tear drop’, gave just as good aerodynamics whilst providing more space for the essential lifting gas.
She did have a short ride in the R101 but it was not ready for its test flight which of course ended fatally at Beauvais, near Paris. She saw the R100 return from its successful first flight, on the day she sailed to the USA. The airship programme ended then.

Nevertheless, this was a fruitful period of research for Hilda and the Aeronautical Journal published her very important paper on the strength of transverse frames of rigid airships in 1930, for which she was the first woman to be awarded the R38 Memorial Prize by the Royal Aeronautical Society. The same year she went to do 2 years of postgraduate study at the Massachusetts Institute of Technology on a Mary Ewart Travelling Scholarship.

Section of the graph from her Master’s thesis

This gave her her first access to wind tunnels and she submitted her thesis on “The Effect of Turbulence on the Drag of Airship Models” to obtain her MA from MIT in 1932. That work took her for a year in Göttingen in Germany, where she conducted aerodynamics research at the Kaiser Wilhelm Gesellschaft für Strömungsforschung with Professor Ludwig Prandtl. Hilda was in Germany as the Nazis were ascending to power and the summer of 1933 must have been terrifying as jewish staff and students were marched out of the university.

However, this was cut short when her mother was taken ill and Hilda was forced to return home to care for her in Yorkshire.

Fortunately, this potentially career-killing domestic obligation was overcome by her former supervisors a the Royal Aircraft Establihsment who, understanding her talents, encouraged her to continue her work from home, sometimes even being able to pay her for small pieces of work. In the 2 years before her mother’s death in 1934, Hilda published 2 papers on streamlining and boundary layer effects and two more in 1935 before the RAE was able to create a post for her to return as a full time Principal Scientific Officer in the aerodynamics department in 1937.

Despite not being employed in the field from 1932-37, she was recognised in a 1934 issue of Flying Magazine as being “…the classic authority on the subject of stresses in transverse frames”. From 1937 onwards she was publishing frequently, up to and even after her death.

Her war work included work on stability analysis of the Hurricane’s rudder. In 1946 she died following an operation and her death was keenly-felt in the aeronautical world as a great loss to the field. Her colleague, W. G. Perrin, noted how she was respected for her painstakingly accurate work. She is buried in her home town, in Market Weighton Cemetery.

After her death, her research and the “Lyon Shape” which she devised were incorporated into the American submarine USS Albacore, which had the prototype streamlined hull form for almost all subsequent US submarines, and those of many other nations. The Lyon Shape may even have been in use in the 1944 German midget submarines (Delfins), which suggests that her brief work at Gottingen may have influenced scientists there. She published a total of 11 papers, some which are still cited today.

USS Albacore

The “Lyon shape” term is widely used in the USA but less known elsewhere. Her 1942 paper, “A theoretical analysis of longitudinal dynamic stability in gliding flight” is considered seminal and continues to be cited in the science of streamlining and boundary layers. Hilda was the lead author with three others as subsidiary co-authors. The paper analysed the dynamic and static stabilities of aircraft when undergoing ‘phugoid’ motion.

This is when the aircraft pitches up and climbs, and then pitches down and descends, accompanied by speeding up and slowing down as it goes “downhill” and “uphill”, and can be the cause of dangerous instability, especially if any of the plane’s control surfaces, such as rudder or ailerons are damaged. Hilda’s paper offered various mechanical solutions to ‘dampen’ this up and down motion and is a key reference in many subsequent papers on phugoid motion problems. Today’s planes have “anti-phugoid” control software based on her work, although it is not always helpful, as in a modern air incident in which knowledge of this ‘phugoid’ motion was implicated. The US Airways Flight 1549 ditched in the Hudson River on January 15, 2009. Its captain, Chesley (“Sully”) Sullenberger, said that the landing could have been less violent had the anti-phugoid software installed on the plane not prevented him from manually getting maximum lift during the four seconds before water impact.

A further legacy was a Hilda Lyon Prize for RAE apprentices which was awarded for some years after her death.

The girl from Market Weighton travelled far but her professional legacy travelled much further and she is now becoming better recognised and becoming a great historical role model for potential young engineers today.

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